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vegeta1138

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January 20th, 2008 16:00

admsnap SQL and multiple LUNs

We have an EMC CX3-10c that hosts our SQL Database. There are 3 Luns. One contains the log (ldf) file, the second contains the primary file group and the third the secondary file group.

Every night we run the following admsnap in a batch file via Windows Scheduled Tasks:

admsnap stop -s LogFile-o j:
admsnap flush -o j:
admsnap start -s LogFile-o j:
admsnap stop -s PrimaryFileGroup-o i:
admsnap flush -o i:
admsnap start -s PrimaryFileGroup-o i:
admsnap stop -s SecondaryFileGropu-o h:
admsnap flush -o h:
admsnap start -s SecondaryFileGroup-o h:

My question is this: If we find ourselves in the unfortunate position of having to do a rollback, will the data be consistent? My concern is that since the log file and database file are so interdependent that the snapshots won't occur in parallel and thus the snapshot would be virtually useless.

The example I' thinking of is that the log LUN is snapped and then a record is inserted then the DB and then the DB lun is snapped.

Is this a valid concern? If so what options (with admsnap) to we have?

Many thanks,

kelleg

6 Operator

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4.5K Posts

January 21st, 2008 09:00

There is a consistant function that is part of snapview. You must use the navicli -snapview command:

naviseccli -h ss1_spa snapview -startsession 2pmsession -lun one
two three -consistent

Please see "EMC® SnapView¿ Command Line Interfaces (CLI)" manual on PowerLink for instructions on using this command (Chapter 4 page 160).

Also see the Administrators guide for SnapView

regards,

glen kelley

AranH1

2.2K Posts

January 21st, 2008 12:00

Glen,
Won't that only provide a crash consistent database and not an application consistent database?

I have SQL databases in our environment and have used at different times snaps, clones, Replication Manager, and RecoverPoint for the replication of these databases. Unless the replication method specifically freezes the database and creates a SQL consistent point in time version of the data, the data will only be crash consistent. SQL can usually recover from crash consistent data but officially Microsoft states that it is not a supported method for disaster recovery.

Replication Manager and RecoverPoint have the ability to create SQL consistent replicas, but with scripting you would have to create a custom script that includes calls to the SQL database to create a SQL consistent replica.

Aran

kelleg

6 Operator

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4.5K Posts

January 21st, 2008 13:00

That is very true - I only pointed to the consistent snap function as a possible way to take a consistent snap on multiple LUNs at the same time.

If the database is not "paused" or put into a mode for recovery, then the consistent snap only provides crash protect. Scripting this is very difficult and I do really not know how this is done.

regards,

glen kelley

dynamox

11 Legend

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20.4K Posts

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87.4K Points

January 22nd, 2008 20:00

we still can't do a consistent fracture with clones in multiple clone groups, can we ?

kelleg

6 Operator

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4.5K Posts

January 23rd, 2008 10:00

I believe that functionality has been in the code since release 19. I just tried three clones, one from one clonegroup and one from a second clonegroup and it worked. In the GUI, hold down the shift key and select the LUNs to fracture then when all highlighted, right-click and select fracture.

regards,

glen

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